Electromagnets

Build A Speaker

Introduction:

A speaker is a device that converts an electronic signal into sound. The speaker you will build (see figure 1) consists of a Styrofoam or paper cup, a coil of wire, a permanent magnet, and a signal source. The electronic signal goes through the coil and creates a varying electromagnet. The attraction and repulsion between the electromagnet and the permanent magnet cause the cup to vibrate and produce sound.

Activity:

Materials:

• 1 permanent magnet
• 2 feet of wire
• sandpaper
• 1 pencil
• tape
• 1 Plastic cup
• 1 signal source
• 1 plug for tape player

Assemble materials as shown in figure 1.

1. Leaving about 5 centimeters on each end, wrap the wire around a pencil to make a wire coil. The coil should be about 1 centimeter in diameter and contain about 50 coils.
2. Scrape the insulation off 1-2 centimeters of the ends of the coil.
3. Tape the coil to the bottom of the plastic cup.
4. Place the cup on the magnet base and tape to wooden dowel.
5. Secure the coil ends to the two wing nuts and attach the ends of the plug (must make contact to complete the circuit.
6. Attach your device.
7. Adjust the apparatus until you get sound coming out of your speaker.

Conclusion:

1. Does the volume control on the tape player work on your speaker? Explain your answer.
2. What kind of sound quality do you get out of your speaker? Compare the loudness and the clarity.
3. How does the sound quality compare with your normal speakers/earbuds?
4. Explain how your speaker reproduces sound.
5. Explain what happens when you place a coil of wire near a permanent magnet.

Practice:

Enrichment:

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